/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: SuballocatedByteVector.java,v 1.2.4.1 2005/09/15 08:15:57 suresh_emailid Exp $
 */
package com.sun.org.apache.xml.internal.utils;

/**
 * A very simple table that stores a list of byte. Very similar API to our
 * IntVector class (same API); different internal storage.
 *
 * This version uses an array-of-arrays solution. Read/write access is thus
 * a bit slower than the simple IntVector, and basic storage is a trifle
 * higher due to the top-level array -- but appending is O(1) fast rather
 * than O(N**2) slow, which will swamp those costs in situations where
 * long vectors are being built up.
 *
 * Known issues:
 *
 * Some methods are private because they haven't yet been tested properly.
 *
 * If an element has not been set (because we skipped it), its value will
 * initially be 0. Shortening the vector does not clear old storage; if you
 * then skip values and setElementAt a higher index again, you may see old data
 * reappear in the truncated-and-restored section. Doing anything else would
 * have performance costs.
 *
 * @xsl.usage internal
 */
public class SuballocatedByteVector {

  /**
   * Size of blocks to allocate
   */
  protected int m_blocksize;

  /**
   * Number of blocks to (over)allocate by
   */
  protected int m_numblocks = 32;

  /**
   * Array of arrays of bytes
   */
  protected byte m_map[][];

  /**
   * Number of bytes in array
   */
  protected int m_firstFree = 0;

  /**
   * "Shortcut" handle to m_map[0]
   */
  protected byte m_map0[];

  /**
   * Default constructor.  Note that the default
   * block size is very small, for small lists.
   */
  public SuballocatedByteVector() {
    this(2048);
  }

  /**
   * Construct a ByteVector, using the given block size.
   *
   * @param blocksize Size of block to allocate
   */
  public SuballocatedByteVector(int blocksize) {
    m_blocksize = blocksize;
    m_map0 = new byte[blocksize];
    m_map = new byte[m_numblocks][];
    m_map[0] = m_map0;
  }

  /**
   * Construct a ByteVector, using the given block size.
   *
   * @param blocksize Size of block to allocate
   */
  public SuballocatedByteVector(int blocksize, int increaseSize) {
    // increaseSize not currently used.
    this(blocksize);
  }


  /**
   * Get the length of the list.
   *
   * @return length of the list
   */
  public int size() {
    return m_firstFree;
  }

  /**
   * Set the length of the list.
   *
   * @return length of the list
   */
  private void setSize(int sz) {
    if (m_firstFree < sz) {
      m_firstFree = sz;
    }
  }

  /**
   * Append a byte onto the vector.
   *
   * @param value Byte to add to the list
   */
  public void addElement(byte value) {
    if (m_firstFree < m_blocksize) {
      m_map0[m_firstFree++] = value;
    } else {
      int index = m_firstFree / m_blocksize;
      int offset = m_firstFree % m_blocksize;
      ++m_firstFree;

      if (index >= m_map.length) {
        int newsize = index + m_numblocks;
        byte[][] newMap = new byte[newsize][];
        System.arraycopy(m_map, 0, newMap, 0, m_map.length);
        m_map = newMap;
      }
      byte[] block = m_map[index];
      if (null == block) {
        block = m_map[index] = new byte[m_blocksize];
      }
      block[offset] = value;
    }
  }

  /**
   * Append several byte values onto the vector.
   *
   * @param value Byte to add to the list
   */
  private void addElements(byte value, int numberOfElements) {
    if (m_firstFree + numberOfElements < m_blocksize) {
      for (int i = 0; i < numberOfElements; i++) {
        m_map0[m_firstFree++] = value;
      }
    } else {
      int index = m_firstFree / m_blocksize;
      int offset = m_firstFree % m_blocksize;
      m_firstFree += numberOfElements;
      while (numberOfElements > 0) {
        if (index >= m_map.length) {
          int newsize = index + m_numblocks;
          byte[][] newMap = new byte[newsize][];
          System.arraycopy(m_map, 0, newMap, 0, m_map.length);
          m_map = newMap;
        }
        byte[] block = m_map[index];
        if (null == block) {
          block = m_map[index] = new byte[m_blocksize];
        }
        int copied = (m_blocksize - offset < numberOfElements)
            ? m_blocksize - offset : numberOfElements;
        numberOfElements -= copied;
        while (copied-- > 0) {
          block[offset++] = value;
        }

        ++index;
        offset = 0;
      }
    }
  }

  /**
   * Append several slots onto the vector, but do not set the values.
   * Note: "Not Set" means the value is unspecified.
   */
  private void addElements(int numberOfElements) {
    int newlen = m_firstFree + numberOfElements;
    if (newlen > m_blocksize) {
      int index = m_firstFree % m_blocksize;
      int newindex = (m_firstFree + numberOfElements) % m_blocksize;
      for (int i = index + 1; i <= newindex; ++i) {
        m_map[i] = new byte[m_blocksize];
      }
    }
    m_firstFree = newlen;
  }

  /**
   * Inserts the specified node in this vector at the specified index.
   * Each component in this vector with an index greater or equal to
   * the specified index is shifted upward to have an index one greater
   * than the value it had previously.
   *
   * Insertion may be an EXPENSIVE operation!
   *
   * @param value Byte to insert
   * @param at Index of where to insert
   */
  private void insertElementAt(byte value, int at) {
    if (at == m_firstFree) {
      addElement(value);
    } else if (at > m_firstFree) {
      int index = at / m_blocksize;
      if (index >= m_map.length) {
        int newsize = index + m_numblocks;
        byte[][] newMap = new byte[newsize][];
        System.arraycopy(m_map, 0, newMap, 0, m_map.length);
        m_map = newMap;
      }
      byte[] block = m_map[index];
      if (null == block) {
        block = m_map[index] = new byte[m_blocksize];
      }
      int offset = at % m_blocksize;
      block[offset] = value;
      m_firstFree = offset + 1;
    } else {
      int index = at / m_blocksize;
      int maxindex = m_firstFree + 1 / m_blocksize;
      ++m_firstFree;
      int offset = at % m_blocksize;
      byte push;

      // ***** Easier to work down from top?
      while (index <= maxindex) {
        int copylen = m_blocksize - offset - 1;
        byte[] block = m_map[index];
        if (null == block) {
          push = 0;
          block = m_map[index] = new byte[m_blocksize];
        } else {
          push = block[m_blocksize - 1];
          System.arraycopy(block, offset, block, offset + 1, copylen);
        }
        block[offset] = value;
        value = push;
        offset = 0;
        ++index;
      }
    }
  }

  /**
   * Wipe it out.
   */
  public void removeAllElements() {
    m_firstFree = 0;
  }

  /**
   * Removes the first occurrence of the argument from this vector.
   * If the object is found in this vector, each component in the vector
   * with an index greater or equal to the object's index is shifted
   * downward to have an index one smaller than the value it had
   * previously.
   *
   * @param s Byte to remove from array
   * @return True if the byte was removed, false if it was not found
   */
  private boolean removeElement(byte s) {
    int at = indexOf(s, 0);
    if (at < 0) {
      return false;
    }
    removeElementAt(at);
    return true;
  }

  /**
   * Deletes the component at the specified index. Each component in
   * this vector with an index greater or equal to the specified
   * index is shifted downward to have an index one smaller than
   * the value it had previously.
   *
   * @param at index of where to remove a byte
   */
  private void removeElementAt(int at) {
    // No point in removing elements that "don't exist"...
    if (at < m_firstFree) {
      int index = at / m_blocksize;
      int maxindex = m_firstFree / m_blocksize;
      int offset = at % m_blocksize;

      while (index <= maxindex) {
        int copylen = m_blocksize - offset - 1;
        byte[] block = m_map[index];
        if (null == block) {
          block = m_map[index] = new byte[m_blocksize];
        } else {
          System.arraycopy(block, offset + 1, block, offset, copylen);
        }
        if (index < maxindex) {
          byte[] next = m_map[index + 1];
          if (next != null) {
            block[m_blocksize - 1] = (next != null) ? next[0] : 0;
          }
        } else {
          block[m_blocksize - 1] = 0;
        }
        offset = 0;
        ++index;
      }
    }
    --m_firstFree;
  }

  /**
   * Sets the component at the specified index of this vector to be the
   * specified object. The previous component at that position is discarded.
   *
   * The index must be a value greater than or equal to 0 and less
   * than the current size of the vector.
   *
   * @param at Index of where to set the object
   */
  public void setElementAt(byte value, int at) {
    if (at < m_blocksize) {
      m_map0[at] = value;
      return;
    }

    int index = at / m_blocksize;
    int offset = at % m_blocksize;

    if (index >= m_map.length) {
      int newsize = index + m_numblocks;
      byte[][] newMap = new byte[newsize][];
      System.arraycopy(m_map, 0, newMap, 0, m_map.length);
      m_map = newMap;
    }

    byte[] block = m_map[index];
    if (null == block) {
      block = m_map[index] = new byte[m_blocksize];
    }
    block[offset] = value;

    if (at >= m_firstFree) {
      m_firstFree = at + 1;
    }
  }

  /**
   * Get the nth element. This is often at the innermost loop of an
   * application, so performance is critical.
   *
   * @param i index of value to get
   * @return value at given index. If that value wasn't previously set, the result is undefined for
   * performance reasons. It may throw an exception (see below), may return zero, or (if setSize has
   * previously been used) may return stale data.
   * @throws ArrayIndexOutOfBoundsException if the index was _clearly_ unreasonable (negative, or
   * past the highest block).
   * @throws NullPointerException if the index points to a block that could have existed (based on
   * the highest index used) but has never had anything set into it. %REVIEW% Could add a catch to
   * create the block in that case, or return 0. Try/Catch is _supposed_ to be nearly free when not
   * thrown to. Do we believe that? Should we have a separate safeElementAt?
   */
  public byte elementAt(int i) {
    // %OPT% Does this really buy us anything? Test versus division for small,
    // test _plus_ division for big docs.
    if (i < m_blocksize) {
      return m_map0[i];
    }

    return m_map[i / m_blocksize][i % m_blocksize];
  }

  /**
   * Tell if the table contains the given node.
   *
   * @param s object to look for
   * @return true if the object is in the list
   */
  private boolean contains(byte s) {
    return (indexOf(s, 0) >= 0);
  }

  /**
   * Searches for the first occurence of the given argument,
   * beginning the search at index, and testing for equality
   * using the equals method.
   *
   * @param elem object to look for
   * @param index Index of where to begin search
   * @return the index of the first occurrence of the object argument in this vector at position
   * index or later in the vector; returns -1 if the object is not found.
   */
  public int indexOf(byte elem, int index) {
    if (index >= m_firstFree) {
      return -1;
    }

    int bindex = index / m_blocksize;
    int boffset = index % m_blocksize;
    int maxindex = m_firstFree / m_blocksize;
    byte[] block;

    for (; bindex < maxindex; ++bindex) {
      block = m_map[bindex];
      if (block != null) {
        for (int offset = boffset; offset < m_blocksize; ++offset) {
          if (block[offset] == elem) {
            return offset + bindex * m_blocksize;
          }
        }
      }
      boffset = 0; // after first
    }
    // Last block may need to stop before end
    int maxoffset = m_firstFree % m_blocksize;
    block = m_map[maxindex];
    for (int offset = boffset; offset < maxoffset; ++offset) {
      if (block[offset] == elem) {
        return offset + maxindex * m_blocksize;
      }
    }

    return -1;
  }

  /**
   * Searches for the first occurence of the given argument,
   * beginning the search at index, and testing for equality
   * using the equals method.
   *
   * @param elem object to look for
   * @return the index of the first occurrence of the object argument in this vector at position
   * index or later in the vector; returns -1 if the object is not found.
   */
  public int indexOf(byte elem) {
    return indexOf(elem, 0);
  }

  /**
   * Searches for the first occurence of the given argument,
   * beginning the search at index, and testing for equality
   * using the equals method.
   *
   * @param elem Object to look for
   * @return the index of the first occurrence of the object argument in this vector at position
   * index or later in the vector; returns -1 if the object is not found.
   */
  private int lastIndexOf(byte elem) {
    int boffset = m_firstFree % m_blocksize;
    for (int index = m_firstFree / m_blocksize;
        index >= 0;
        --index) {
      byte[] block = m_map[index];
      if (block != null) {
        for (int offset = boffset; offset >= 0; --offset) {
          if (block[offset] == elem) {
            return offset + index * m_blocksize;
          }
        }
      }
      boffset = 0; // after first
    }
    return -1;
  }

}
